Normally, the following demands are made on such an attachment device: the attachment must connect the steering wheel to the steering shaft in a positive and secure way, since accidental loosening of this connection could have grave consequences. Furthermore, the connection must be detachable, so that, for example, the steering wheel can be replaced. Finally, it must also be possible to adjust the angular alignment of the steering wheel in relation to the steering shaft.
With the usual method of attaching the steering wheel to the steering shaft, a spline shaft connection is used to produce the joint-rotation shaft/hub connection. By fitting the hub with internal splines onto the end of the steering shaft provided with external splines, a joint-rotation connection is achieved between steering wheel and steering shaft, the angular alignment of which can be adjusted. In order to secure the hub on the steering shaft in the axial direction of the latter, a nut is screwed onto a thread extension formed on the named end of the steering s haft from the inside of the hub, this nut clamping the hub to the steering shaft. This attaches the steering wheel to the shaft in a positive and secure manner.
As a consequence of the growing safety awareness in recent time, gas bag restraint systems are being increasingly used, which are located on the driver's side inside the hub of the steering wheel. In the interests of efficient assembly, such a gas bag restraint system should already be fitted in the steering wheel when supplied to the vehicle manufacturer. However, the consequence of this is that, as a result of the components of the gas bag restraint system mounted inside the hub of the steering wheel, access to a clamping element located inside the hub is difficult or even impossible.